While the achievement could happen naturally, I kept screwing up after two or three foul balls so wanted to get this out of the way.
Quick Play>Practice
Choose OFFENSE and any team
Set EGO to 0
For pitches one and two, as soon as the pitcher releases the ball, hold
to swing very early and start with an 0-2 count. Now instead of trying to intentionally hit a foul ball, put your cursor all the way down and to the right. Then swing with normal timing and hopefully the pitch will be misaligned just enough to cause a foul ball.